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A276733 Composite numbers n such that 2^lpf(n) == 2 (mod n), where lpf(n) = A020639(n). 1
341, 1247, 1387, 2047, 2701, 3277, 3683, 4033, 4369, 4681, 5461, 5963, 7957, 8321, 9017, 9211, 10261, 13747, 14351, 14491, 15709, 17593, 18721, 19951, 20191, 23377, 24929, 25351, 29041, 31417, 31609, 31621, 33227, 35333, 37901, 42799, 45761, 46513, 49141, 49601, 49981 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Super-Poulet numbers A050217 is a subsequence.

From Robert Israel, Sep 16 2016: (Start)

If p is a Wieferich prime (A001220), p^2 is in this sequence.

If p is a non-Wieferich prime, there are terms of the sequence divisible by p iff p < A006530(2^p-2). Is the latter true for all primes p except 2,3,5,7 and 13? (End)

LINKS

Robert Israel, Table of n, a(n) for n = 1..1000

MAPLE

filter:= n -> not isprime(n) and 2 &^ min(numtheory:-factorset(n)) - 2 mod n = 0:

select(filter, [seq(i, i=3..100000, 2)]); # Robert Israel, Sep 16 2016

PROG

(PARI) lista(nn) = forcomposite(n=2, nn, if (Mod(2, n)^factor(n)[1, 1] == Mod(2, n), print1(n, ", ")); ); \\ Michel Marcus, Sep 16 2016

CROSSREFS

Cf. A006530, A020639, A050217.

Sequence in context: A083876 A068216 A038473 * A050217 A214305 A086837

Adjacent sequences:  A276730 A276731 A276732 * A276734 A276735 A276736

KEYWORD

nonn

AUTHOR

Thomas Ordowski, Sep 16 2016

EXTENSIONS

More terms from Michel Marcus, Sep 16 2016

STATUS

approved

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Last modified August 8 05:25 EDT 2020. Contains 336290 sequences. (Running on oeis4.)